LONDON – There’s a dead rat at the heart of a new exhibition mounted by august auction house Sotheby’s.

Stuffed and sporting a backpack and a spray can, the rodent is the creation-cum-alter ego of Banksy, the anonymous street artist turned art-world superstar.

It’s a sign of his status that Sotheby’s is behind one of the largest-ever Banksy exhibitions, a display of kissing policemen, placard-wearing chimpanzees and smiley-faced riot police spanning much of the artist’s career. Some of the works originally sold for as little as $84. Now, prices range from $6,700 to more than $840,000.

Banksy is not involved in the show, which is being billed as an “unauthorized retrospective.” It has been assembled by his former agent Steve Lazarides, who first met Banksy in the 1990s in their hometown of Bristol in southwest England.

Lazarides took a paint-filled fire extinguisher to the gallery’s white walls to make it look less like an alien environment for graffiti art. But, he conceded Friday, “It’s completely paradoxical for me to be here – for the work to be here.”

“It’s in a space it almost shouldn’t be and viewed in a way it was never intended,” he said. “But I think that’s part of the fun.”

The 70 paintings, prints and sculptures, owned by Lazarides and other collectors, display Banksy’s subversive – if not always subtle – humor. Winston Churchill sports a Mohawk haircut; genteel pensioners play lawn bowls with fizzing bombs; a ballerina breathes through a gas mask; a hungry child with an empty bowl wears a Burger King hat.

Several early works feature police officers – the bane of Banksy’s existence as a young street artist. For others, he has altered existing paintings: Van Gogh’s sunflowers have withered and died; flying saucers disrupt a maritime scene.

Some have not been seen in public for years, including the rat, in a glass case bearing the words “Our Time Will Come.” Banksy installed it in 2004 in London’s Natural History Museum as hundreds of visitors and staff walked by.

Banksy works have fetched as much as $1.8 million at auction, so it’s no surprise that several of his outdoor works have recently – and controversially – been stripped from walls and sold for high prices.

None of the pieces in the London show was originally street art, and Sotheby’s contemporary art chief Cheyenne Westphal said all have been endorsed as genuine by Pest Control, Banksy’s authentication service.

“Works that are on the street don’t get certificates,” she said. “They’re there to be enjoyed, they’re there to be seen, but they’re not there to be resold again.”

As his career has bloomed, Banksy has left his spray-painted mark worldwide, from the streets of New York to the Israel-Palestine separation wall.

As for big gallery shows like this, Lazarides said, “He hates it.”

Lazarides, who parted company with Banksy several years ago, takes a different view.

“The show being here at Sotheby’s is almost a validation of the whole scene,” he said. “When we were doing this 15 years ago, everyone told us this was impossible – no one would buy the work, it was a fad, it would disappear.

“People tend to forget that (Jean-Michel) Basquiat and Keith Haring were graffiti artists first. This is just following on from a rich tradition.”